Thermogauge resistor



ug 139 W4@ K. SCHWARTZWALDER ET AL 2,211,153

THERMOGAUGE RESISTOR med Jan. s, 193s COPPE l? coppe@ s/mL :mentors y copper it was found that after the piece of cop- Patented Aug. 13, 1940 PATENT OFFICE THERMQGAUGE RESISTOR Karl Schwartzwalder and Robert H. Bigler,

Flint, Mich., assignors to-General Motors Corporation, Detroit, Mich., a corporation of Dela- Ware l Application January 3,

6 Claims.

This invention relates to temperature indicators and. has particular reference to the engine unit of an electric telemetric system adapted for use in connection with the internal combustion engine used on an automobile.

The characteristic of a thin layer of copper oxide to decrease. in electrical resistance with an Aincrease in temperature is known and the engine unit of the present invention makes use of this characteristic. In conducting experiments with different ways of making and retaining a thin layer or film of copper oxide on a sheet of per has been given a thin coating of oxide by placingit in a suitable atmosphere at a relatively hightemperature, this coating of oxide chips off as the copper coated article cooled to normal temperature. This chipping off made the copper piece unsuitable for use in a temperature indicator.

In order to maintain a good film of copper oxide on the copper, experiments were conducted to maintain the oxide film in such shape that after cooling the copper oxide would not chip from the copper. Accordingly, a metallic shell was used in which a rod of copper coated with copper oxide was inserted and while the copper rod and the copper oxide were still in the same heated condition they were when removed from the oxidizing furnace, the rod was placed in the shell and the space between the rod and the shell was filled by pouring in a molten metal.

unit cooled the metal surrounded the copper oxide and prevented its chipping and maintained a good film of oxide between the copper rod and the cast metal.

Many experiments have been conducted with different types of metal for a filler between the tube and the copper oxide but the best metal for the purpose was found to be bismuth which has the characteristic of expanding on cooling and thus tightly and completely filling the space be' tween the shell and the copper oxide layer and tightly holding the copper oxide in place on the copper rod. It was found that if the shell so constructed is placed inside an internal combustion engine where it is subject to the changes in temperature of the water cooling system of the engine. and the unit connected in a circuit having a differential galvanometer at the instrument boa-rd of the vehicle, that temperatures can be read directly from the dial of the galvanometer which has been graduated to read in tempera- -tures instead of units of electrical current.

On the drawing:

1938, Serial No. 183,102

Figure 1 is a partial view of an automotive vehicle showing the invention applied.

Figure 2 is an enlarged sectional detailed view through the applied unit and taken on the line 2 2 of Figure 1.

Figure 3 is a sectional view of the unit itself separated from the engine, but suggesting a different filler metal.

On the drawing the numeral 2 indicates the vehicle as a whole. The vehicle has the roof 4, the cowlB, the hood 8, the chassis ill, the internal combustionl engine i2 having the head I4 and l the starter motor I6 associated therewith.' The clutch housing is indicated at I8 and the transmission housing at 20. The instrument board of the vehicle is shown at 22.

In the head I4 of the engine there is mounted as at 24 the engine unit of the heat indicating system. This unit is connected by a wire 26 to a differential galvanometer 28 mounted on the instrument board 22. A wire 30 connects the galvanometer 28 with the ignition switch 32 operated by a key 34. A wire 36 connects the ignition switch to the battery 38 mounted on and grounded at 40 to the frame lil;

Referring to Figure 3, the engine unit 42 of the invention is shown. This unit comprises the outer metallic tubular shell 44 preferably of copper, the cast metal ller 46, and the copper rod 48 which has a coating of copper oxide 50 thereon. Both the shell 44 and the rod 48 are round in cross section. The shell 44 is closed and rounded at its inner end as shown at 52 and is open and outwardly flared into a flange at its upper end as indicated at 54. The flange 54 vis return bent as shown at 56. 'I'he rod 48 extends a considerable' distance beyond the mouth or open end 58 of the shell and has its end threaded as at 6|).

Referring to Figure 2 in which the uni-t is shown as applied, the parts designated by numerals in Figure 2 are similarly designated in Figure 3 except that the filling 46 in Figure 3 is represented by the bismuth 46' in Figure 2. Other than bismuth and zinc, other metals such as antimony, lead, cadmium, solder, etc, may be used. The copper oxide coated rod 48 is at a temperature of between 200 and 500 centigrade when the metal 46 or 46 is cast into the shell 44. 'I'his temperature is desirable because it prevents the chipping on' of the copper oxide vcoating when the metal is cast into the shell.

The engine head|4 has a threaded opening 62 therein and at the bottom of the threaded opening there is the inclined shoulder 64 on which there. is adapted to be received the ared ange 54 of the unit 42. A head 66 having an inner tapered end 68 is screw-threaded into the threaded opening 62 in the cylinder block and by tightly screwing the head in place the inclined surfaces formed by the parts 54, 56,164, and 68 will be held tightly in contact to prevent the leakage of any Water from the engine. If desired, gaskets may be interposed to insure a tight seal.

The head 66 is preferably hexagonal in'shape to enable the easy application of a tool and it has a central bore 10 which is considerably larger than thev rod 48 and through which the rod extends so that th'e threaded end 60 projects outwardly from the outer at surface 1I of the head 66. A cone of insulating material 12 fits into the conical central part 14 of the head 66 at the position shown in Fig. 2. The wire 26 is loopedl as shown at 82 and surrounds the threaded end 60. A second nut 84 is screwed onto the threaded end 60 and holds the loop tightly between the nuts and 84.

The operation of the device is as follows: When the water circulating system of the engine is cold the metal of the unit 42 of course will be cold and the dial of the galvanometer 28 will read at the starting point of the scale which. for instance, may be at F. As the water takes up heat from the engine the unit 42 will be heated and cause a change in the electrical resistance characteristic of the copper oxide lm 50. This decrease in resistance of the film will allow the current to pass through the battery, the'switch 32, the differential galvanometer 28, the lead 26, the rod 48, and the copper oxide film 58. From the nlm 50 the current will pass through the filler 46, shell 42, and the engine block back to the battery at 46. 'Ihechange in the electrical conductivity of the 'of oxide will cause a greater amount of current to pass through the system and cause' a greater deflection of the needle of the galvanometer 28, or to record the change of temperature in accordance with the change of current passing through the system.

We claim: A

1. In a unit for an electric telemetric temperature indicating system, an outer protector shell open at one end and closed atthe other and adapted to be tted to the device the temperature of which is to be indicated, a copper rod in the shell and spaced from the walls thereof, a coating of copper oxide on the rod, and a filler of bismuth cast into and completely lling the space between the copper oxide coating and the shell.

.2. In a unit for an electric telemetric'temperature indicating system, an o'uter protector shell open at one end and closed at the other and adapted to be tted to the device the`temperature of which is to be indicated, a. copper rod, part of the rod extending into the shell and spaced therefrom and having a coating of copper oxide thereon, the other end of `therod projecting outside the shell, and a filler of bismuth cast into and completely lling the space between the copper oxide and the shell. 3. In a unit for an electric telemetric temperature indicating system, an outer protector shell open at one end and closed at the other and adapted to be tted to the device the tempera- -ture of which is to be indicated,` a head secured to the shellv and adapted to hold the shell in place, a copper 'rod in the shell and spaced therefrom, a coating of copper oxide on the rod, and a filler of bismuth cast into and completely ll.- ing the space between the copper oxide and the Shell.

4. In a unit for an electric telemetric temperature indicating system, an outer protector shell open at one end and closed at-the other and adapted to be iitted to the device the temperature of which is to be indicated, a head secured to the shell and adapted to hold the shell in place,

a copper rod in the shell and spaced therefrom,l

said rod projecting through said head, a coating of copper oxide on the rod, and a ller of bismuth cast into and completely lling the space between the copper oxide and the shell.

5. In a unit for an electric telemetric temperature indicating system, an outer protector shell open at one end and closed at the other and oxide on the rod, and a ller of bismuth cast into and completely lling the space between the cop-v per oxide andthe shell.

6. In a unit for an electric telemetric temperature indicating system; an outer protector shell open at one end and closed at the other and adapted to be fitted to the device the temperature of which is to be determined, a copper rod in the shell and spaced therefrom, said rod extending short of the bottom of the shell at one end and projecting outside the shell at the other end, a coating of copper oxide on the part of the rod within `the shell, and a. lling of bismuth cast into the shell to ll completely the space between the copper oxide and the shell.

i KARL SCHWARTZWALDER.

ROBERT H. BIGLEB. 

